Lookup HTTP connection via message server

Experts:

When creating a New Connection Entry to J2EE, SAP doc provides detailed

steps for 2 types of connection:

1) Lookup HTTP connection via message server

2) Using a Direct Connection to the Dispatcher

However, SAP does tell what is the difference between above 2 options, i.e.

what is the connection mechanism for each type?

Would you please help explain ?

Thnaks a lot!